This is a brief discussion about tire wear problems and what is the probable cause of certain kinds of wear which can be seen on your tires. As you read this, please keep in mind that the essential term here is probable ... it is possible there might be other causes but in the experience shown through countless cases and controlled laboratory experiments these are the causes which are most likely.
If you notice that both the shoulders or outside edges of a tire's tread is more worn than the area between, the most likely reason is the tires have been running with less pressure than is ideally required for that tire. The ideal pressure is that which is determined by your vehicle manufacturer under normal load and using a certain sized tire.
If your conditions, such as the weight you are carrying in the vehicle or the size and type of tires is different from what the manufacturer recommends, the inflation pressure they recommend may have to be adjusted, because when a tire is under inflated the center part of the tread tends to lift up off the road and the entire weight is carried on the shoulders, causing this area to wear more rapidly.
Other causes might be frequent and repeated turning at high speeds, the incorrect matching of wheels and tires, or a lack of tire rotation.
The opposite type of tread wear problem --the center being more worn than the shoulders-- is caused by too-much air pressure, or over-inflation. When too much air is in a tire it begins to bulge just like a balloon -- it gets rounder and this forces the edges of the tire tread to lift and receive less wear than the center area. Also incorrect matching of tires with the wheels and lack of rotation can contribute to this kind of wear.
Greater wear on one shoulder than on the other shoulder is a sign of wheel alignment problems. The specialist will likely look first at the camber angle, which is the setting of the wheel in relation to the vertical position. Depending on whether the inside edge or the outside edge is more highly worn will depend on the positive or negative camber misalignment. This problem is also contributed to by a less than ideal frequency of tire rotation.
Much less common than the three problems already mentioned is a wear pattern which shows greater wear in certain spots around the circumference to the tire, rather than even wear all around. This can be more complicated to solve since it could be caused by problems in the suspension, the wheel assembly or brakes. Unbalanced tires, too much runout of the wheels, sudden braking or spinning of wheels in acceleration and under inflation can also contribute to this kind of wear.
Wear in diagonal strips across the tire is more rare b but can be caused by faulty suspension, rotating parts or brake parts, improper wheel alignment a dynamic imbalance of tire/rim assembly, tires that haven't been rotated recently and under-inflation.
A wear pattern called feathering can often be detected by running your fingers over the tire tread. You can often feel a very fine ridge on one side of the tire ribs which are not on the other edge. This is a classic sign of a wheel alignment caused by an improper toe angle or much less commonly by a bent wheel axle.
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